1. Field of the Invention
The present description relates generally to semiconductor devices and, more specifically, to deposition of layers containing titanium and aluminum.
2. Description of the Related Art
A typical metal-oxide-semiconductor (MOS) device includes a gate oxide layer and a poly-Si (polysilicon) layer that are patterned into a gate using lithography and etching techniques. Ion implantation may then be used to form source/drain regions in the substrate beside the gate. However, poly-Si is not an ideal gate material in advanced node applications because of its high resistance. Furthermore, poly-Si can induce gate depletion and cause voltage loss. As such, metal gates have been proposed for many advanced MOS processes. However, many materials of the metal gates may negatively impact the work functions of NMOS gates and PMOS gates. The work function characteristics often need to be adjusted by providing work function adjusting layers of material.
The present disclosure is directed to various methods of forming semiconductor devices that involves the deposition of layers containing titanium and aluminum that may solve or reduce one or more of the problems identified above.